In recent years, organic light-emitting diodes have been attracting attention in view of luminescence technique for next generation displays and illumination. In the early study of organic light-emitting diodes, fluorescence has been mainly used. However, in recent years, an organic light-emitting diode utilizing phosphorescence which exhibits higher internal quantum efficiency has been attracting attention.
Mainstream of emissive layers utilizing phosphorescence in recent years are those in which a host material comprising an organic material is doped with an emissive metal complex including iridium or platinum as a central metal.
However, an iridium complex and platinum complex are rare metals and are therefore expensive, giving rise to the problem that organic light-emitting diodes using these rare metals are increased in cost. Copper complexes, on the other hand, likewise emit phosphorescent light and are inexpensive, so that they are expected to reduce the production cost.
For example, JP-A 2008-179697 (Kokai) discloses an organic light-emitting diode using a copper complex as a light-emitting material. However, the copper complex used here has the problem that the synthetic method is complicated.